1. Field of the Invention
The present invention relates to a lamp for radiation of a warning signal in all directions around a lamp axis, with a base body fixable at a mounting location and an optical basic arrangement comprising an annular support element and an inner and outer drum optical system, wherein a number of lighting means is arranged on the support element in annular distribution, each of the lighting means radiates light radially outwardly with respect to the lamp axis in a three-dimensional angular range which, around the lamp axis, covers an azimuth angle substantially smaller than 360 degrees and, relative to the lamp axis, covers a polar angle substantially greater than a desired polar angular range in which the warning signal is to be radiated about a mean polar direction, light (central light) radiated by the lighting means relative to the lamp axis in a central polar angular range containing the mean polar direction passes through the outer drum optical system, and the arrangement of the lighting means on the support element, the arrangement of the support element and the outer drum optical system and the construction of the outer drum optical system are so adapted to one another that the central light radiated from the lighting means is after issue from the outer drum optical system radiated in polar direction within the desired polar angular range.
2. Prior Art
A lamp of that kind is known from DE-U-203 05 625 of the applicant.
The known lamp already works very well. In particular, it combines a relatively simple construction with outstanding water tightness and a high level of mechanical reliability and robustness.
The lighting means of the known lamp are usually 5 millimeter light-emitting diodes which on the basis of an optical system integrated in the light-emitting diodes have a beam opening angle of approximately 30 degrees. A light intensity of the lamp of approximately 150 to 200 candela can usually be achieved with use of light-emitting diodes of that kind.
In order to also satisfy international regulations in the field of air travel, lamps have to attain considerably higher lighting intensities. This cannot be readily managed with conventional light-emitting diodes.
Recently, new high-output light-emitting diodes, which radiate a substantially greater amount of light than the light-emitting diodes used hitherto, are available on the market. These high-output light-emitting diodes have, however, a radiation characteristic of approximately 180 degrees. They thus radiate their light substantially hemispherically. If high-output light-emitting diodes of that kind were to be employed in known lamps a not inappreciable proportion of the light would be radiated outside the desired polar angular range.
A lamp for radiation of a warning signal in all directions around the lamp axis is known from US-A-2003/072150, which comprises a base body fixable at a mounting location and an optical basic arrangement, wherein the optical basic arrangement comprises an annular support element and a drum optical system. A plurality of mounting means is arranged on the support element in annular distribution. The support element carries, inter alia, the drum optical system. Each of the lighting means radiates light with respect to the lamp axis radially outwardly in a three-dimensional angular range which, around the lamp axis, covers an azimuth angle substantially smaller than 360 degrees and, relative to the lamp axis, a polar angle substantially greater than a desired polar angular range in which the warning signal is to be radiated about a mean polar direction. Light (central light) radiated by the lighting means relative to the lamp axis in a central polar angular range containing the mean polar direction passes through the drum optical system. The central light contains light (inner central light) radiated in a polar middle region containing the mean polar direction and light (outer central light) radiated in two polar outside regions each adjoining, in polar direction, the polar middle region on a respective side. The outer central light between entry into the drum optical system and issue from the drum optical system is incident on a drum reflector which is a component of the drum optical system. It is reflected there. After passing through the drum optical system the light still passes through an outer cover, which, however, no longer influences the radiation characteristic of the light. The arrangement of the lighting means and the drum optical system on the support element as well as the construction of the drum optical system (inclusive of the drum reflector) are matched to one another in such a manner that the light is radiated within the desired polar angular range about the mean polar direction already after issue from the drum optical system.
A headlight is known from U.S. Pat. No. 1,888,995. The headlight comprises an inner reflector, an outer reflector and an optical system. The inner reflector is a component of the optical system. A lighting means which substantially radiates light to all sides is arranged on the optical axis of the headlight. Light radiated by the lighting means relative to the optical axis in a central angular range containing the optical axis passes through the optical system without prior incidence on the reflectors. Light radiated by the lighting means in a middle angular region initially enters the optical system, then passes to the inner reflector of the optical system, is reflected there in a direction running substantially parallel to the optical axis and then issues from the optical system. The middle angular range adjoins the central angular range. Light radiated by the lighting means in an outer angular range is initially reflected by the outer reflector in a direction running substantially parallel to the optical axis. It then passes through the optical system. The outer angular range adjoins the middle angular range. The arrangement of the lighting means, reflectors and optical system is so matched to one another that all the light radiated by the lighting means is radiated from the headlight in a small angular range about the optical axis.